What I also appreciate about Mailfence is that they stick to using standard protocols. Protonmail needs an intermediary layer to provide IMAP services for instance if I recall correctly. Perhaps they (Protonmail) do this to arguably offer better encryption services, but to me email is not very secure to begin with, no matter what you do. You’ll always have your messages pass through other people’s servers and systems and not all your recipients will be comfortable with PGP or s/MIME. I love email as an OG federated service though, despite what some may consider flaws in this modern age. It’s such a core and empowering technology of the internet!